Patent GB-1399783-A (GB)
Title: Automatic viscometer with multiple capillaries
IPC: G01N11/06
Filed: 1973-06-19
Abstract: 1399783 Automatic viscosimeter MOBIL OIL CORP 19 June 1973 [19 June 1972] 28990/73 Heading G1S An automatic viscosimeter comprises a tube 132 having three capillary portions 134, 136 and 138, of different diameters, the capillaries being arranged vertically in order of decreasing diameter up the tube, and means for automatically selecting the appropiate capillary for measuring the viscosity of a sample. Above each capillary there is provided a measurement bulb 140, 142, 144 and an overflow bulb 141, 143, 145. Above and below each measurement bulb is provided a level sensor 150-155 which may be a thermistor Fig. 4, (not shown), a photo-cell or a spark detector. The tube is surrounded by a constant temperature water jacket which may be of a double walled construction, Fig. 8 (not shown). Samples to be tested are supplied in containers 113 mounted on a turn-table rotatable in steps by pneumatic ram 205. An air heater 128 may be used to pre-heat samples on the turn-table. At the test station, a container 113 is lifted from the turn-table by a pneumatic lift 240, 135 into a carriage 125, the container entering a pre-heat jacket 122. Carriage 125 is movable by pneumatic ram 200 to the right in Fig.1 along a rail 126 to bring the container 113 under the tube, waste receptacle 127 also being mounted on the carriage. The rail 126 is part of a frame 131 movable vertically by a pneumatic ram 201 to dip the end of the tube into the sample in the container. The movements of the container are monitored by a series of micro-switches 220, 226. The upper end of the tube is connected to a valve system for applying vacuum atmosphere, nitrogen and solvent to the tube. The system comprises solenoid valves 166- 171, vacuum regulator 202, and vacuum reservoirs 177, 178 connected to the regulator via restrictors 175, 176. A controller 174, which may be a computer controls the operation of the viscosimeter to automatically measure the viscosities of the samples in the containers 113 in turn. With a container 113 in position about the bottom end of the tube, vacuum is applied to the tube via valves 168, 167 and 166, and via the restrictor 176 and the reservoir 178, to fill the tube, the purpose of reservoir 178 being to fill the tip portion 133 of the tube almost immediately. The controller 174 measures the time the sample takes to reach detector 151 and compares this with a predetermined time interval. If the time taken is longer than the predetermined interval, the viscosity of the sample is high and will be measured using the lowest, coarsest capillary 134. If the time taken is shorter than the predetermined interval, the viscosity of the sample is too low to be measured with the lowest capillary and the sample continues to be drawn up the tube, the time taken by the sample to reach the detector 153 being compared with a second predetermined interval to determine whether the middle capillary 136 or the upper capillary 138 will be used to measure the viscosity. Assuming that the lowest capillary 134 has been selected for a measurement, the vacuum is shut off when the sample reaches detector 151, and air is momentarily admitted to prevent further sample being drawn into the tube. If the sample level falls below detector 151, vacuum is applied via restrictor 175 to correct this. After a period to achieve temperature stabilization of the sample, valve 173 operates to connect the tube to reservoir 177 to raise the level of the sample slightly, the container 13 is lowered and the tip 33 allowed to drain, and the top of the tube is connected to atmosphere. The time taken for the sample to travel between detectors 151, 150 is measured by the controller. A duplicate run may then be carried out before the tube is washed with solvent and dried with nitrogen. The tip 133 is sprayed with solvent during the washing operation by lines 203. Two separate viscometer tube arrangements may be associated with the turn-table and may operate at the same or different temperatures.